In recent years, as machines that perform bag making and packaging by making bags and filling the insides of those bags with contents such as snack foods, there have been bag making and packaging machines. For example, in vertical bag making and packaging machines called form-fill-seal machines, a packaging material that is a sheet-like film is formed into a tubular shape by a former and a tube, and the overlapping vertical edges of the tubular packaging material are heat-sealed (heat-welded) to form a tubular packaging material by a vertical sealing mechanism. Then, the inside of the tubular packaging material that eventually becomes made into bags is filled with contents from the tube, heat sealing is performed across the upper end portion of one bag and the lower end portion of the trailing bag by a transverse sealing mechanism below the tube, and thereafter the center of that heat-sealed portion (transverse seal portion) is cut by cutters.
Further, among such bag making and packaging machines, there are machines that perform bag making processing while forming gussets (fold portions) in positions that become the side portions of the bags.
For example, in Japanese Laid-Open Patent Application Publication No. 7-156908 published on Jun. 20, 1995, there is disclosed a vertical form-fill-seal machine that forms gussets in side portions of bags by using air cylinders to drive a left-and-right pair of gusset plates into and out of a packaging material that is intermittently conveyed.